1. Field of the Invention
The present invention relates to a motor in which common side coil end parts of stator coils are electrically connected collectively to each other through a common processing. In addition, the present invention relates to a motor stator comprising a plurality of divided cores joined in a circular ring-shaped manner, and more specifically to a motor stator, as well as to its manufacturing method, in which a stator core, comprising divided cores arranged in a circular ring-shaped manner on the inside of a cylindrical motor case, is fixed.
2. Description of Related Art
Generally, in a motor having a plurality of phases, an outside lead-out side end section of a stator coil for each phase wound on a stator core is led out to the outer side for each phase and connected to an outside lead-out terminal, while a common side coil end section at the other end of the stator core for each phase is rendered a so-called common processing, so that each common side coil end section led out for each phase from a winding part of the corresponding stator coil is electrically connected collectively with other common side coil end sections to a common terminal through soldering.
For example, in an inner rotor-type brushless DC motor shown in FIG. 13, a stator coil 3 for each phase is wound around a bobbin 2 attached to a stator core 1, and a common side coil end part led out from a winding part of the stator coil 3 is led out towards the bottom of the drawing. In the meantime, at the bottom end side of the bobbin 2 is attached a common terminal body 4, which comprises a ring-shaped connection material as shown in FIG. 14. After each common side coil end part 3a led out towards the bottom is inserted through one of a plurality of holes 4a formed in the common terminal body 4, the common processing is rendered.
Additionally, a known motor stator is composed by joining, in a circular ring-shaped manner, outer circumference parts of divided cores on which salient poles are formed. Compared to winding stator coils around salient poles of a unitary structure core, the winding work is easier and the space factor of the stator coils increases with the divided cores, which improves motor efficiency.
In a motor stator formed from divided cores, a method has been proposed to shrink-fit a ring-shaped body (a motor case) on the outside of divided cores arranged in a circular ring-shaped manner in order to mutually fix the divided cores.
However, the common processing of the stator coils 3 that was in practice conventionally involves a large number of parts, and therefore increases costs, due to the fact that the common terminal body 4 is used. Furthermore, due to the fact that all common side coil end parts 3a that are led out for the common processing must be individually inserted through the holes 4a of the common terminal body 4, workability during assembly is not favorable.
In a conventional method to fix divided cores through shrink-fitting, when the ring-shaped body's inner diameter dimension allowance is large or its precision of out-of-roundness poor, it becomes impossible to press the ring-shaped body around the circular outer circumference surface of the divided cores arranged in a circular ring-shaped manner during shrink-fitting, leading to a possibility of a shrink-fit failure. In order to machine the inner circumference surface of the ring-shaped body to a high precision, NC lace machining must be done, which increases the parts cost.
When the inner circumference dimension of the ring-shaped body that serves to fix the divided cores is large, shrink-fitting is easy since the overall thermal expansion amount is large even at a relatively low temperature. However, when its inner diameter dimension is small, shrink-fitting is difficult since the overall thermal expansion amount is small even when the ring-shaped body is heated to a high temperature. As a result, there is a problem in that shrink-fitting is not suitable when the ring-shaped body has a small inner diameter dimension.
Furthermore, when the ring-shaped body that serves to fix the divided cores is made of a material with high specific heat, such as iron, shrink-fitting is easy since the material does not cool easily. However, when the material has low specific heat and cools easily, such as aluminum, shrink-fitting is difficult. This restricts the material of the ring-shaped body that can be used to fix the divided cores.